package com.tjhk.java.tech.io;

import java.io.*;
import java.nio.IntBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.util.Arrays;

public class MappedIO {
    private static int numOfInts = 4_000_000;
    private static int numOfBuffInts = 100_000;
    private abstract static class Tester{
        private String name;

        public Tester(String name) {
            this.name = name;
        }

        public void runTest(){
            System.out.println(name+":");
            long start = System.nanoTime();
            run();
            double duration = System.nanoTime() - start;
            System.out.format("%.3f%n",duration/1.0e9);
        }
        public abstract void run();
    }
    private static Tester[] tests = {
            new Tester("Stream Write") {
                @Override
                public void run() {
                    try(
                        DataOutputStream dos = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(new File("temp.tmp"))))
                    ) {
                        for (int i = 0; i < numOfInts; i++) {
                            dos.writeInt(i);
                        }
                    }catch (IOException e){
                        throw new RuntimeException(e);
                    }
                }
            },
            new Tester("Mapped Writer") {
                @Override
                public void run() {
                    try(
                            FileChannel fc = new RandomAccessFile("temp.tmp","rw").getChannel()
                    ) {
                       IntBuffer buffer =fc.map(FileChannel.MapMode.READ_WRITE,0,fc.size()).asIntBuffer();
                        for (int i = 0; i < numOfBuffInts; i++) {
                            buffer.put(i);
                        }
                    }catch (IOException e){
                        throw new RuntimeException(e);
                    }
                }
            },
            new Tester("Stream Read") {
                @Override
                public void run() {
                    try (
                        DataInputStream dis = new DataInputStream(new BufferedInputStream(new FileInputStream("temp.tmp")))
                    ){
                        for (int i = 0; i < numOfInts; i++) {
                            dis.readInt();
                        }
                    } catch (IOException e) {
                        throw new RuntimeException(e);
                    }
                }
            },
            new Tester("Mapped Read") {
                @Override
                public void run() {
                    try(
                        FileChannel fc = new FileInputStream("temp.tmp").getChannel()
                    ) {
                        IntBuffer buffer = fc.map(FileChannel.MapMode.READ_ONLY,0,fc.size()).asIntBuffer();
                        for (int i = 0; i < numOfBuffInts; i++) {
                            buffer.get();
                        }
                    } catch (IOException e) {
                        throw new RuntimeException(e);
                    }
                }
            },
            new Tester("Stream Read/Write") {
                @Override
                public void run() {
                    try(
                       RandomAccessFile raf = new RandomAccessFile(new File("temp.tmp"),"rw")
                    ) {
                        raf.writeInt(1);
                        for (int i = 0; i < numOfBuffInts; i++) {
                            raf.seek(raf.length() - 4);
                            raf.writeInt(raf.readInt());
                        }
                    } catch (IOException e) {
                        throw new RuntimeException(e);
                    }
                }
            },
            new Tester("Mapped Read/Write") {
                @Override
                public void run() {
                    try(
                        FileChannel fc = new RandomAccessFile(new File("temp.tmp"),"rw").getChannel()
                    ) {
                        IntBuffer buffer= fc.map(FileChannel.MapMode.READ_WRITE,0,fc.size()).asIntBuffer();
                        buffer.put(0);
                        for (int i = 1; i < numOfBuffInts; i++) {
                            buffer.put(buffer.get(i-1));
                        }
                    } catch (IOException e) {
                        throw new RuntimeException(e);
                    }
                }
            }
    };

    public static void main(String[] args) {
        Arrays.stream(tests).forEach(Tester::runTest);
    }
}
